Polyphenol is one kind of plant component having a plurality of phenolic hydroxy groups in a molecule. Polyphenol is contained in almost all plants, and the number thereof reaches 5,000 species or more. Polyphenol is known as an antioxidative component that is produced by the plant for protecting its own self from active oxygen.
Green tea which is a beverage enjoyed for a long time contains a large amount of polyphenols, which are generically referred to as tea catechins, having a 3-hydroxyflavan structure. The tea catechins are known to have a great number of action useful for health, such as antioxidative action, sterilizing action, anticancer action, antitumor action, hypotensive action, blood sugar level elevation inhibitory action, body fat-reducing action and anti-fatigue action.
Moreover, a chlorogenic acid compound (chlorogenic acids) that is first isolated from coffee beans and is an ester compound of cinnamic acid or a derivative thereof and quinic acid is also one kind of polyphenol. This chlorogenic acid compound is known to have action of inhibiting elevation of a postprandial blood sugar level, or the like.
However, it is known that, even if polyphenol such as the tea catechins and the chlorogenic acid compound is orally ingested, absorptivity into a living body is low. For example, when a human or a rat orally ingests epigallocatechin gallate that is one kind of tea catechins and a water-soluble low-molecular weight substance, a migration rate thereof into blood is as significantly low as about 2% (for example, see Non-Patent Literatures 1 and 2).
Therefore, a great number of researches for improving absorption of polyphenol such as catechins and the chlorogenic acid compound into the living body have been conducted. For example, Patent literatures 1 and 2 describe an absorption enhancer for a catechin compound, containing serine, aspartic acid, malic acid, capric acid, lauric acid, grapefruit juice, succinic acid, cysteine, asparagine, isoleucine, pinitol, or the like, as an active ingredient.